DATOS RELATIVOS A LA FICHA DE EVALUACIÓN

within the nuclear power plant area. Movement in this area will be restricted. There will be no impact on water traffic running on waterways indicated in nautical charts.

7.9 Noise

7.9.1 Present state

No operations causing significant noise are currently taking place in the vicinity of the planned power plant location on the Hanhikivi headland. The location near the sea is rather favora- ble in terms of dispersion of noise. In particular, dispersion of noise along the water surface enables low-frequency noise to spread over considerable distances during calm weather.

Below is a brief presentation of general information con- cerning industrial noise, road traffic noise, and guideline values for noise.

7.9.1.1 Industrial noise

Industrial noise is mostly noise emanating from static noise sources, such as industrial plants. However, it is common to include all the noise caused by operations taking place in

the industrial area, such as noise caused by forklift trucks and truck loaders, in the scope of industrial noise. Indus- trial noise often contains narrow-band sound components. In these components, the sound concentrates within a lim- ited frequency range, and pure tones (i.e. sounds contain- ing only one frequency) may clearly be distinguished from the noise. Transformers or fans and pumps operated at even rotation speeds and designed so that the air passing through them flows directly into the surrounding atmosphere often emit a narrow-band operating sound. In nuclear power plants, such components include transformers and ventila- tion-related fans. Various silencer solutions are commonly applied to decrease the sound level of air fans. In new power plants, the silencers are installed in the construc- tion phase. Furthermore, impulse-like sounds may be heard locally during the construction of the plant. In these cases, the noise is caused by forceful impact-type events.

7.9.1.2 Road traffic noise

Factors affecting the level of noise generated by motor vehicle traffic include the speed of the vehicles, traffic volumes, the share of heavy vehicles, and the properties of the road. The

Figure 7-31. Traffic volumes in 2025 and the increase in traffic volumes due to the operation of the nuclear power plant according to the Finnish Road Administration’s traffic increase estimate.

168 7 Assessment methods, the present state of the environment and the assessed environmental impacts

noise generally occurs in the form of an even wide-band hum, from which the sound of individual vehicles may occasionally be distinguished. In addition to the noise output level, the fac- tors affecting the noise level in a certain location include the distance between the location and the traffic route, buildings and other obstacles, the shape of the terrain, and water areas and other reflective surfaces. The doubling of traffic volume increases noise level by 3 dB. Correspondingly, the increase of speed level from 50 km/h to 80 km/h increases the noise level by 4–5 dB. Road traffic noise is commonly reduced by means of noise barriers and prevented through land use planning.

7.9.1.3 Guideline values for noise

The main objectives and measures of noise prevention are presented in the Environmental Protection Act and the Environmental Protection Decree, both of which entered into force on March 1, 2000. Guideline values for the A-weighted equivalent sound levels L_Aeq are presented in Government Decision (993/1992). The guideline for residen- tial areas, recreational areas located within or in the imme- diate vicinity of populated areas, and areas accommodating care or educational institutes is that the ambient noise level may not exceed the daytime guideline value of 55 dB(A) (7 a.m. – 10 p.m.) or the night-time guideline value of 50 dB(A) (10 p.m. – 7 a.m.). In recreational residence areas and nature conservation areas, the corresponding guideline values are 45 dB(A) in the daytime and 40 dB(A) in the night time. The night-time guideline value is not applied in nature conser- vation areas that are not commonly used for recreational purposes or observation of nature at night.

The purpose of the guideline values for noise is to pre- vent the adverse impacts of noise on people. According to the explanatory memorandum for the Government Deci- sion on the guideline values for noise (Ympäristöministeriö 1992), the purpose of the guideline values set for nature conservation areas is to guarantee an opportunity to enjoy the sounds of nature. Any marked access routes or paths must be taken into account when applying the guide- line values in nature conservation areas. According to the explanatory memorandum, meeting the guideline values in all parts of a nature conservation area is not required (Ympäristöministeriö 1992).

7.9.2 Assessment methods

In order to assess the noise impacts, the noise caused by the nuclear power plant, and the dispersion thereof, were modeled using a common Nordic industrial and road traffic noise model. The model considers the geometrical diver- gence loss, differences in the altitude of the terrain, build- ings and other reflective surfaces, and the acoustic effects of ground surface and atmospheric noise.

The dispersion map included in the noise model cal- culates the average sound level contours at the interval of five decibels (dB) on the basis of the selected initial values. Water and road surfaces and the plant area were generally defined as hard ground surfaces. This, for its part, elimi- nated the contribution of ground attenuation to the sum

of individual attenuations considered in the calculation. The dispersion of noise is calculated in accordance with the modeling algorithm. Furthermore, it is calculated conser- vatively, assuming that the environmental condition points are favorable for the dispersion of noise (including a light downwind from the noise source to each calculation point). The greater the distance from the noise source, the greater the effect of annual variation in weather and, in particular, the wind direction, on the actual noise level in the area will be. Thus, as the distance from the noise sources increases, the calculation uncertainty increases as well; at the distance of one kilometer, it is approximately ±3 dB.

Both estimated values and values measured from corre- sponding sound sources were utilized in the noise calculation to determine the initial values for the sound power levels of noise sources (overall level and spectral distribution). The sound power levels of noise sources located inside buildings were defined in terms of how much noise is carried from the inside to the outside, assuming that the wall materials have sound reduction capabilities in accordance with the proper- ties of their component substances. As a rule, the entire wall area and roof of buildings were defined as surface sound sources. Furthermore, some of the sound sources were defined as directional sound sources. The estimation of the sound lev- els of fans located on roofs was based on the assumption that the fans are point sound sources. As detailed plant design or noise prevention planning has not yet been carried out, the current sound source descriptions are preliminary.

Construction-phase noise was modeled to represent the conditions during the first years of construction, when the noise levels are at their highest. At that point, the most sig- nificant noise sources will be the rock crushing plant, truck loaders, and traffic.

The noise caused during the construction of the reactor building, the turbine building, and the auxiliary buildings (offices, emergency power generators) was modeled using an area source covering the whole plant site. The overall sound power level of the noise LAeq was determined to be

107 dB(A) + 5 dB at the distance of one meter from the area source (including the impulsiveness correction). This cor- responds well to the actual situation, although the sound level of the noise, and in particular, the maximum level, will be momentarily exceeded due to impact-type noise events, the occurrence of which is common during construction operations.

The rock crushing plant was modeled as an individual operation in the noise calculation. The overall sound power level of 120 dB(A) + 5 dB of rock crushing plant includes the operation of truck loaders. The sound power spectrum was estimated on the basis of available measurement results from a corresponding plant. As the sound emanating from the crushing plant will be rather loud and, due to the opera- tion of truck loaders, occasionally impulsive in nature, rock piles higher than the plant itself have been included in the construction-phase calculation models. The purpose of the rock piles is to function as noise barriers directing the noise away from the most noise-sensitive areas.

Road traffic volumes during the construction phase and normal operation were estimated for noise calculation

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